Method of forming a reproducting of an article



Jan. 27, 1942. R. w. ERDLE ETAL 2,271,454

METHOD OF FORMING A REPRODUCTION OF AN ARTICLE Filed June 25, 1938 2Sheets-Sheet 1 m 3 ab, 65 U. w I 6 n a i Ill/l/l 'IIIIII/ YIIIII/II/ lmwllmzand g Jan. 27, 1942. R. w. ERDLE ETAL METHOD OF FORMING AREPRODUCTION OF AN ARTICLE Filed June 25, 1958 2 Sheets-Sheet 2 vPatented Jan. 27, 1942 METHOD OF FORMING A REPRODUCTION OF AN ARTICLEReiner W. Erdle, Chicago, Ill., Henry Soller, Brooklyn, N. Y., and PaulH. Beier, Chicago, Ill., assignors to Dental Research Corporation,

Chicago, Ill., a corporation of Illinois Application June 25, 1938,Serial No. 215,810

27 Claims. (Cl. 18-55) This invention relates to a method of forming areproduction of an article upon the same scale or upon a reduced or anenlarged scale.

While the invention is particularly useful in making artificial teeth,it is not limited to such use but may be employed for formingreproductions of other articles as suitable and desired.

In making artificial teeth, the tooth porcelain or other tooth materialwith which it is desired to reproduce definite selected teeth shrinksupon firing same to bring it to hard and vitrified form. As a result, ifit is desired to duplicate any selected tooth in its exact size, it isnecessary to produce an unfired tooth sufliciently oversize to allow forthis shrinkage. If it is desired to make an oversize or an undersizereproduction of the original tooth it is necessary to take into accountthe desired final size of the reproduction and the shrinkage which takesplace upon firing the porcelain. For example, if it is desired that thefired porcelain reproduction be larger than the original tooth and theporcelain has a linear shrinkage of 12% upon firing, it is necessary tohave an unfired specimen which is sufficiently larger than the originalto take carev of the shrinkage and also the amount of oversize desired.Upon firing, the increased size allowed for shrinkage is lost and thefired reproduction will be oversize the desired amount. Should it bedesired to produce a fired reproduction smaller than the original,the'unfired specimen will be larger than the original, but the oversizewill be less than the amount allowed for shrinkage where a duplicateupon the same scale is desired, so that after the loss in size uponfiring the reproduction will be the desired amount smaller than theoriginal.

It is known in the art to use enlarged master patterns for reproducingthe desired teeth, and

various schemes have been provided for securing the enlargement of thesepatterns. According to one scheme, enlarging machines of many and varieddesigns have been employed, and in other cases skilled artisans havecarved or otherwise fashioned the enlarged master patterns for use informing the desired reproductions.

keep in adjustment, it being particularly difficult to keep the cutterand tracer in accurate positive relation to each other, and continuousadjustments are required to get down to final cutting, all of whichintroduces many possible errors.

By using a refractory material consisting principally of ground quartzmixed with an agent, such as soda-glass, patterns which will be enlargedby conversion of the quartz upon firing may be formed, but thisnecessitates a multi These prior schemes, however, are incapable ofgetting true and accurate reproduction of extremely fine character,especially with reference to the definite lines and other details whichchar- 50 acterize the natural teeth. Moreover, these prior schemesrequire considerable time to produce the enlargement, and they cannotproduce more than a single unit at a time. In the case of enplicity ofsteps because of the inability to secure the desired amount of expansionin one step. Where a multiplicity of steps are necessary to secure thedesired amount of enlargement, the cost and time required are increasedand the fine details desired in the reproduction are lost.

One of the main objects of our invention is to provide an improvedmethod of forming reproductions of articles and, more particularly inthe illustrated embodiment of the invention, an improved method offorming very accurate reproductions of natural teeth, whichreproductions may be upon the same scale or upon a reduced or enlargedscale, and follow faithfully all definite lines and other details whichcharaca step in the method of forming the reproduction which comprisesforming an impression, usually in the form of a flexible sheath, overthe original tooth or other article, removing the sheath from thearticle, expanding the same to secure the desired enlargement thereof,and forming in the expanded sheath an enlarged pattern for use inproducing, for example, an unfired tooth oversize in amount to take careof the shrinkage of the porcelain or other material upon firing, or withthe oversize in amount to produce any desired enlargement or reductionin size of the final reproduction.

Another object is to secure various degrees of enlargement of anyselected article or master over a wide range without loss of accuracy inthe reproduction and without the necessity of repeated steps to obtainthe desired degree of enlargement. If desired, however, the methodoflarging machines, these machines are diflicult to 55 enlargementherein disclosed may be carried out in repeated steps within the scopeof the present invention.

Another object is to keep the expanded sheath in the desired expandedstate during the formation of the enlarged pattern therein.

Another object is to produce repeatedly any intermediate stage ofenlargement with exactness.

showing the first step of setting up the natural tooth or other articleon a layer of material such as modeling clay;

Figure 2 is a similar view showing the next step of forming the flexiblesheath over the tooth;

Figure 3 shows the flexible sheath in section after removal from thetooth;

Figure 4 shows more or less diagrammatically the step of expanding theflexible sheath;

Figure 5 shows the step of forming enlarged stone patterns in aplurality of enlarged flexible sheaths;

Figure 6 is a view of one of the enlarged stone patterns after removalfrom the flexible sheath;

Figure 7 shows the step of forming a second flexible sheath upon theenlarged stone pattern;

Figure 8 shows the step of forming a wax pattern in the second flexiblesheath;

Figure 9 shows the step of investing the wax pattern and the manner offorming an enlarged master metal pattern;

Figure 10 is a view of the enlarged master metal pattern;

Figure 11 shows the step of forming the flexible mold over the enlargedmaster metal pattern;

Figure 12 shows the step of forming the enlarged uniired porcelain toothin the flexible mold;

Figures 13 and 14 show an alternative manner of forming the flexiblesheath over the natural tooth or other article or original pattern; and

Figures 15, 16 and 17 show a method of making the enlarged master metalpattern directly in the enlarged flexible sheath formed over the naturaltooth or other article or original pattern.

Referring now to the drawings, the first step in the illustratedembodiment of the invention is to set up, as desired, the natural tooth5 or other article or original pattern which it is desired to reproduce,for example on a layer of material such as modeling clay,'as indicatedat 6 in Figures 1 and 2. The root portions 1 of the tooth may beembedded in the material 6, as shown, for the purpose of supporting thetooth in the desired position. Of course the tooth or other article maybe set up and supported in any other suitable manner.

The next step in the process is to form a flexible sheath 8 over the.article. While various sheath materials are contemplated as willhereinafter appear, this material is preferably a rubber latex materialin the form of a liquid or. semi-liquid rubber latex solution, of whichthere are a number on the market.

The latex material is preferably sprayed upon the tooth i as by means ofa spray gun indicated more or less diagrammatically at I in Figure 2,but it is to be understood that other methods, such as painting ordipping, may be used to produce a suitable flexible negative over theselected patterm Where the sheath I is formed by spraying, painting, ordipping, successive coats of the latex material are preferably appliedto the tooth or other article, each coat being dried out by means of ajet of air or otherwise, until a sheath or shell I is built up of suchthickness that it retains its shape when set or coagulated and removedfrom the article I. The sheath I preferably has a generally uniform wallthickness. A suitable thickness has been found to be about of an inch,although the sheath may be thicker or thinner as desired. The latexmaterial lends itself admirably to application by spraying, and thespraying of the material against the natural tooth or other article 5reproduces extremely accurately on the inner surface of the sheath I,which contacts the article I, all details of said article. The flexiblesheath I is preferably provided with an integral flange II formed duringformation of the sheath.

Upon completing the formation of the sheath I to the desired thicknessand after it is dried out and coagulated to form the rubber shell, thisshell is removed from the original pattern by stripping it therefrom. Weflnd that allowing the sheath to set over night produces the desired setor coagulation of the sheath and allows it to reach its full elasticstrength, but this, of course, may vary. The flexibility of the rubbersheath permits its removal from the article 5 notwithstanding undercutsand other formations which might otherwise prevent such removal. Therubber shell or sheath I which now retains its shape after removal fromthe article 5 defines a cavity or matrix H which is a true negative ofthe natural tooth or original pattern 5, and produces faithfully alldeflnite lines and other details which characterize the originalpattern.

The next step is to treat the flexible sheath I with an agent which willexpand the sheath to enlarged size. 'This is preferably accomplished byproviding a bath II of the desired agent in a glass or other suitablecontainer Ii closed at the top by a cover II, and placing the sheath Iin this bath II. The sheath I absorbs the agent i4, and, by thisabsorption, swells or expands to increased size. If the wall thicknessof the sheath is substantially uniform, the expansion is substantiallyuniform, and the enlargement of the cavity or matrix I I produced byexpansion of the sheath is an extremely accurate reproduction of alldefinite lines and other details of the natural tooth or other article Ion an enlarged scale. The spraying of the material forming the sheathmakes it possible expeditiously to secure the desired uniformity in thewall thickness of the sheath. Care should be taken to see that theflexible sheath is placed in the bath II in such position that no air isentrapped, and in such manner that the agent may be absorbedsubstantially equally along all surfaces of the sheath I. A base II ofcotton or other suitable material under the flexiblesheath serves thispurpose.

It has been found that many organic solvents are well adapted to serveas expanding agents, as will hereinafter appear.

. For example, chloroform is an exceedingly satisfactory solvent for thepurpose described, but other solvents and other agents are contemplatedwithin the scope of the present invention. Where chloroform is used asthe solvent, the amount of expansion of the sheath is preferablycontrolled by diluting the expanding liquid or solvent with a liquidwhich may be mixed with the expanding liquid or solvent to reduce thesheath expanding action thereof. Alcohol and acetone are suitableliquids for this purpose as they have no appreciable effect inthemselves in producing expansion, the physical properties of alcoholmaking it more suitable than acetone. Other substances for reducing theactivity of the expanding liquid are contemplated within the scope ofthe present invention. Such largement follows a curve from which-it ispossible to know in advance by the percentage of liquid mixture whatpercentage of expansion will occur when the sheath is immersed therein.Curves have been plotted for the different sheath materials and liquids,but it is not believed necessary to incorporate the same herein. Uponevaporation of the expanding liquid mixture from the sheath material thesheath shrinks to substantially the original size.

The full possible degree of enlargement for any particular expandingmixture occurs in about two hours, and after that the liquid does notproduce any substantial further enlargement but holds the flexiblesheath in this expandedstate. This is ideal because it means that inthis way the amount of enlargement of the sheath not only follows acurve from which it is possible to know in advance what percentage ofexpansion will occur, but the amount of enlargement is not a function oftime, provided a sufilcient period has been allowed for completeabsorption of the expanding mixture. As a result, we may repeatedlysecure any intermediate stage of enlargement with the same exactness asthe full enlargement, if the same sheath .material and expanding mixtureare used. Any desired lesser amount of enlargement is secured bycorrespondingly increasing the percentage of alcoholor other liquid forreducing the expanding action-with respect to the percentage of theactive solvent, and any desired greater amount of enlargement is securedby correspondingly decreasing the percentage of this other liquid withrespect to the percentage of active solvent.

It has been found that when the flexible sheath I is stripped from thetooth I there is substantially a 2% reduction in the size of the sheathdue to the tension therein. It is therefore desirable in carrying out,ur process to enlarge the sheath an amount to take care of this 2%' lossin sheath size and the 12% or other shrinkage of the porcelain infiring, as well as the amount of enlargement or reduction in size wherean enlargement or reduction is desired. Of course, if the pattern orreproduction is to be formed on the same scale asthe original, the

control the expansion as above set forth, produces a reproduction about81% larger than the original article or pattern, and immersion in carbontetrachloride for about two hours produces an en argement of about 91%.The P the selected solvent. This method of controlling centages are, ofcourse, too great if an exact scale reproduction of the natural tooth isdesired wherev the necessary expansion of the sheath would beapproximately 14%, to overcome the 2% loss in sheath size and a 12%shrinkage loss in the firing of the porcelain. However, even withoutdiluting the solvent or expanding liquid, after about two hours nofurther expansion of the sheath takes place and consequently thepercentages 81% and 91%, less the 12% shrinkage loss and the other 2%loss, represent substantially the upper limits of enlargement by asingle step using chloroform and carbon tetrachloride, respectively.Greater enlargements are possible, of course, by repeating the enlargingprocess-that is, by enlarging one sheath, forming a pattern therein, andthen forming a second sheath aroundthis pattern and enlarging the secondsheath. Any desired number of such repeated enlargements may be employedwithin the scope of the present invention.

For example, an expanding mixture of 150 parts chloroform and 100 partsalcohol produces about 28% enlargement of the resulting reproduction,and the enlargement is an exact reproduction of the original, with thefinest lines and other details faithfully reproduced. The mixture ofchloroform and alcohol, in general, provides a more accurate control ofthe amount of expansion than a mixture of carbon tetrachloride andalcohol.

Another example of sheath material and solvent for expanding thsame'according to the present invention employs highly refined gelatineglue as the sheath material, and water for expanding the same. Thissheath material is prepared by mixing two pounds of the gelatinousmaterial with 1400 cc. of water, and heating at In immersing a sheath ofthis material in water to expand the sheath, the water bath ispreferably kept at a temperature of about 1 C. because the gelatine willtend to dissolve when the bath becomes warm. If the gelatine sheath isexpanded in a solution of alum and water, an enlarged sheath is producedwhich is not quite so sensitive to temperature changes.

Any other rubber material which, when set, is pliable and soft, and infact any other flexible material which may be expanded in accordancewith the present invention, is contemplated within the scope of theappended claims. The solvent may be chloroform'or' carbon tetrachlorideas hereinbefore referred to, or it may be carbon bisulphide, benzine,petroleum, ether, turpentine, or any other petroleum product or anyorganic or other suitable solvent.

The present invention also contemplates the use of the element of timeas a means of obtainmg any desired amount of enlargement of the sheathfrom zero to the maximum enlargement that can be obtained by the-solventused with the sheath material. By this means the amount of enlargementdue to immersion of the flexible sheath in the selected solvent isvaried-by allowing the sheath to remain in the solvent for variousperiods of time, from about, five minutes to two hours. This manner ofcontrolling the amount of enlargement is possible because of therelation of the amount of enlargement-with respect to the time ofimmersion of the sheath in the amount of enlargement does not have allof the advantages of the method of controlling the enlargement by theamount of dilution of the expanding liquid with a liquid or othersubstance which will reduce the activity thereof, but it may be employedand therefore is contemplated within the scope of the appended claims.

If it is desired to produce a. reproduction of the original articlewhich is, for example, 6% larger than the original, the total necessarysheath expansion may be readily calculated, and from this the strengthof the necessary expanding liquid can be determined, or, where time isrelied on to control the amount of expansion, the amount of time thesheath is immersed in the expanding I sheath, and subsequently sets to ahard condition.

To. prevent shrinking of the sheath 8 due to evaporation of the solventtherefrom during the introduction of the dental stone into the sheath,and prior to setting of the stone pattern 20, we expose the externalsurface of the sheath to a liquid for preventing evaporation of thesolvent from the enlarged sheath during formation of the enlarged stonepattern in the sheath. Otherwise the shrinking of the sheath whichfollows evaporation of the solvent therefrom would exert pressure on theplastic or semi-plastic stone and cause the production of a stonepattern smaller than the fully expanded sheath.

The exposure of the external surface of the sheath to a liquid forpreventing evaporation of the solvent from the sheath may beaccomplished by suspending a plurality of sheaths 8 by the flanges ii!in openings 22 in a metal plate 23 supported in a container 24 in raisedposition by members 25 as shown in Figure 5.

The container 24 contains a bath of liquid'26 which covers the externalsurfaces of the enlarged sheaths 8 and prevents evaporation of thesolvent from the sheaths. This liquid 28 may be the same as the liquidused as the solvent for expanding the sheaths, or it may be water or anyother liquid immiscible with the solvent and which will not have anydeleterious action upon the sheath material.

After the dental stone pattern 20 has set, the sheath 8 and stoneenlargement are removed from the rack shown in Figure 5 and preferablyallowed to stand in air for about one half hour 'or until the rubbersheath has recovered its full elasticity, whereupon the sheath 8 isstripped from the enlarged stone pattern 20. The stone pattern 20 is nowa very accurate reproduction of the original article 5 on enlargedscale. The sheath 8 will return to substantially the original size whenstripped from the pattern 20, i. e., to a size 2% smaller than theoriginal tooth 5, and has all of its original properties, including thecapability of repeated use for future enlargement without sacrifice ofdetails in the enlarged reproductions.

The next step in the embodiment of the invention illustrated in Figures1 to 12, inclusive, is to form a second flexible sheath 3!) over thestone pattern 23. This second sheath 30 may be formed of the samematerial and in the same when not expanded, does not shrink except forthe slight inherent tension within the sheath, since it is formed toenlarged size over the enlarged stone pattern.

A pattern 32 of wax or other material that can be eliminated from aninvestment by heat is then formed in the enlarged flexible sheath 30.This wax pattern 32 is then placed in an investment flask or ring 34(Figure 9) and embedded in investment material 38 to form a refractorymold. After the ring 34 has been filled with investment material withthe sprue or gate forming part projecting therefrom, the investmentmaterial is set and the wax pattern is eliminated by heat. as well knownin the art. A suitable metal is then introduced in molten conditionthrough the gate 36, and upon solidification forms the master metalpattern 38 which is to the desired enlarged scale and corrwponds exactlywith the details of the original tooth 5. Upon completion of theenlarged master metal pattern 38 the investment material is broken awayand the sprue is cut off or otherwise removed, leaving the enlargedmaster metal pattern 38 as shown in Figure 10.

The master metal pattern 38 is then placed in position as shown inFigure 11 upon a suitable base 40 and within a flask 4| provided at thetop with suitable openings 42, and a flexible mold material 43 is pouredinto the flask 4| through one or more of the openings 42 over thepattern 38 and preferably to a level substantially filling the fiask 4|.The openings 42 permit the escape of air.

The flexible mold material43 is then allowed to set to the permanentflexible stage, as by cooling, and forms a flexible mold having a cavity44 which is an exact negative of the tooth 5 on the desired or selectedenlarged scale. The inner mold surface 44 is continuous throughout andwithout parting lines or the like, and forms an exact negativereproduction of all lines and other details of the tooth or otherarticle 5.

The flexible mold material is preferably rubber or a plasticized vinylchloride compound, but it is to be understood that gelatine, glue, andany other suitable flexible and preferably resilient material may beused within the scope of the present invention. Upon hardening of themold body 43, the flask 4| is removed, and the master metal pattern isremoved from the mold cavity 44, flexing of the mold 43 permitting suchremoval notwithstanding undercut or projecting parts on the master metalpattern.

Porcelain or other suitable material employed for forming the green orunfired artificial porcelain tooth indicated at 48 in Figure 12. Thetooth material is finely ground, moistened with water or mixed with achemically setting binder, and is packed compactly in the mold cavity44,

preferably by prolonged vertical vibration which porcelain tooth thusformed is sufliciently firm to permit removal from the mold and handlingbefore fire-hardening.

After completion of the packing of the porcelain and formation of thegreen porcelain tooth 4| in the mold It, the unflred and enlargedporcelain tooth 48 is removed from the flexible mold ll, flexing of themold permitting such removal notwithstanding undercuts, projections andthe like. The unfired and enlarged porcelain tooth is then dried andfired to the desired point of vitrification. It is to be noted that thethoroughness and density of the packing of the porcelain are important.It directly influences the linear shrinkage of the porcelain uponfire-hardening. If the packing is poor, the porcelain particles are notcompacted to the greatest degree, and the resulting shrinkage is greaterthan the shrinkage of about 12% which proper packing secures.

When the "green" porcelain tooth is fired to the desired point ofvitrification, the shrinkage which occurs brings the fire-hardened andvitrifled artificial tooth to the selected size, and it followsaccurately all details of the original tooth- 5.

resisting temperatures of over 300 F. The split mold I0 is separated inorder to remove the encased pattern 20, and the sheath 8 is strippedfrom the pattern.

The flexible sheath I is then reinserted into position in the split moldIll as shown in Figure 16, and in this way there is produced a rubber orsheath lined split mold, the inner surface ll of which accuratelyreproduces the details of the original tooth 5, or its enlargement.'Into this mold is pouredor cast any metal or metal alloy,

preferably which has a melting point below the temperature which willdestroy the sheath 0.

There are many methods by which the metal may be cast or poured into themold, but any method which produces an exact reproduction is sure headwhich produces good results. To do The manner of forming the mold ll,packing more fully disclosed and claimed in the copending application ofReiner W. Erdle, Serial No.

101,740, flied September 21, 1936.

While spraying of the latex or other sheath material to form the desiredsheaths as herein described has been found to be preferable, it is to beunderstood that other methods of forming these sheaths may be employedwithin the scope of the present invention.

For example, the original tooth or original pattern 5' may be set upupon a layer of modeling clay 8' as before, but within a suitable metalring as shown in Figure 13. The ring '0 is then fllled with rubber latexor other suitable sheath material which, upon setting, coagulating, orhardening, for example by air cooling to the desired flexiblecondition,/forms a soft form of the pattern. The material is cutaway andleaves the flexible shell or sheath 86.

Another method of forming an enlarged metal master pattern of thenatural tooth or other article 5 is illustrated more or lessdiagrammatically in Figures 15, 16 and 17. This method may be used withlow temperature fusing metals, i. e., metals which fuse at temperatureswhich will not destroy the flexible sheath.

This latter method comprises taking the enlarged flexible sheath asshown at O in Figure 5, with theset pattern 20 of dental stone therein,and forming a stone mold around the sheath encased pattern as shown atIll. The mold 10 may be split at H in such manner that the stone pattern20 may be removed from the mold l0 notwithstanding undercut surfaces ofthe sheath encased pattern. Any other suitable material than dentalstone may be employed for forming the mold 10, preferably a materialcapable of metal head portion along the line 0-0.

this, a copper or other suitable tube 15 is placed over the moldopening, and the metal is poured into the mold and up into the tube 15.

. This creates a pressure head, and results in good casting. The moldmay or may not be cold. Upon completion of the enlarged metal masterpattem'" the sheath 0 may beremoved and the pattern cut away or removedfrom the solidified The pressure may also be obtained by means of anycasting machine which imparts a centrifugal force to the metal, and inthis way forces the metal into the mold under the desired pressure.

Instead of making the mold around the sheath encased pattern 2|, thepattern may be removed from'the sheath and the mold made around thesheath, in which case splitting of the mold is not necessary, orthe'sheath may be otherwise suping-metal directly into the same.

The surface of the enlarged metal master pattern may be burnished tobring about a shine and smoothness to the surface. This affords anexcellent. manner of providing good permanent metal masters suitable forthepreparation of the flexible molds, and which master metal patternsmay be used repeatedly.

While we have illustrated and described the invention, particularly withreference to making a flexible negative, it is to be understood that aflexible positive may be made and this flexible positive thereuponenlarged by methods similar to those herein described.

There are several ways of employing this flexible positive method. Forinstance, a flexible positive may be made by taking a plaster or otherimpression of the original object. A rubber shell may then be built upon the inside of the impression, usin'ggrease or a suitable separatingmedium if necessary, and then after it has been built up to sufllcientthickness it could be stripped out and then expanded. This enlargedpositive may thereupon be embedded in an investment and, after theinvestment has set, may be withdrawnor burned out-and a suitable metalthereupon cast into the cavity, thus producing an enlarged metalpattern.

Another method would be to electroplate a metal shell over the outsideof the original pattern, or, to avoid undercuts, a coating could beelectroplated onto a flexible duplicate of the original pattern. Thepattern could thereupon be removed and the electroplated shell could bereenforced by embedding it in metal, or plaster,

or the like, and a soft grade of flexible rubber could thereupon bepacked into the cavity and vulcanized, thus resulting in a rubberpositive which could be expanded in the usual manner. This could beinvested and cast as already described.

For expediency, the several views of the drawings are not shown on thesame scale and, therefore, do not show by comparative dimensions theenlargement obtained in accordance with the present invention.

We do not intend to be limited to the precise details or steps shown anddescribed.

We claim:

1. The steps in the method of forming a reproduction of an article whichcomprise forming against the article a body of material adapted toabsorb a fluid and to be changed in size by the influence of theabsorbed fluid thereby reproducing in said body the contourcharacteristics and details of the article, treating said body with afluid adapted to be absorbed by said body to change the size of saidbody by the influence of the absorbed fluid while maintaining thecontour characteristics and the details of the article reproduced insaid body.

' said body.

3. The steps in the method of forming a reproduction of an article whichcomprise forming against the article a flexible body having thecharacteristic of expanding to enlarged size by absorption of a solventthereby reproducing in said body the contour characteristics and detailsof the article, and treating the flexible body with a solvent to expandthe flexible body to enlarged size 'while maintaining its contourcharacteristics and the details of the article on an enlarged scale.

4. The steps in the method of forming a reproduction of an article whichcomprise forming against the article a flexible body having thecharacteristic of expanding to enlarged size by absorption of a solventthereby reproducing in said body the contour characteristics and detailsof the article, and treating the flexible body with a solvent, dilutedwith an inert substance to control the amount of enlargement, to expandthe flexible body to enlarged size while maintaining its contourcharacteristics and the details of the article on an enlarged scale.

5. The steps in the method of forming a reproduction of an article whichcomprise applying a rubber latex material over the article and allowingsame to set to form a flexible sheath, removing the sheath from thearticle, and treating the sheath with an organic solvent for expandingthe sheath to enlarged size to form an enlarged matrix which is a truenegative of the article on enlarged scale.

6. The steps in the method of forming a reproduction of an article whichcomprise forming over the article a flexible sheath of a material havingthe characteristic of expanding to enlarged size by absorption of asolvent, removing over the article a flexible sheath of a material thesheath from the article, immersing the sheath in a solvent to expand thesheath to enlarged size, and controlling the amount of expansion or thesheath by the interval of time the sheath is immersed in said solvent.

7. The steps in the method otforming a reproduction of an article whichcomprise forming having the characteristic oi! expanding to enlargedsize by absorption of a solvent, removing the sheath from the article,and treating the sheath with a solvent, diluted with an inert substanceto control the amount of enlargement, to expand the sheath to enlargedsize.

8. The steps in the method of forming a reproduction or'an article,which comprise applying a rubber latex material over the article andallowing same to set to form a flexible sheath, removing the sheath fromthe article, and treating the sheath with chloroform to expand thesheath to enlarged size.

9. The steps in the method of forming a reproduction of an article whichcomprise applying a rubber latex material over the article and I saidbody the contour characteristics and details of the article, treatingthe flexible body with a solvent to expand the flexible body to enlargedsize, and controlling the amount of expansion of said body by the amountor time the body is acted upon by said solvent while maintaining thecontour characteristics and the details oi'the article on an enlargedscale.

11. The steps in the method 01 forming a reproduction of an articlewhich comprise forming against the article a body or material adapted toabsorb a fluid and to be changed in size by the influence of theabsorbed fluid thereby reproducing in said body the contourcharacteristics and details of the article, treating said body with afluid adapted to be absorbed by said body to change the size of saidbody by the influence of the absorbed fluid while maintaining thecontour characteristics and the details of the article reproduced insaid body, and forming against the surface of the body which was formedagainst the article a reproduction of the article of a size differentfrom the size 01' the article.

12. The steps in the method of forming a reproduction or an articlewhich comprise forming against the article a body of flexible materialadapted to absorb a fluid and to be changed in size by the influence ofthe absorbed fluid thereby reproducing in said body the contourcharacteristics and details of the article, treating said body with afluid adapted to be absorbed by said body to change the size of body bythe influence of the absorbed fluid while maintaining the contourcharacteristics and the details of the article reproduced in said body.

13. The steps in the method of forming a reproduction of an articlewhich comprise applying a rubber latex material against the article andallowing same to set to form a flexible body having reproduced thereinthe contour characteristics and details of the article, and treating theflexible body with chloroform mixed with a substance to control theamount of enlargement, to

expand the flexible body to enlarged size while maintaining the contourcharacteristics and details of the articleon an enlarged scale. I

15. The steps in the method of forming a reproduction of an articlewhich comprise forming against the article a body of flexible materialadapted to absorb a liquid and to be expanded by the influence of theabsorbed liquid thereby reproducing in said body the contourcharacteristics and details of the article, treating said body with aliquid adapted to be absorbed by said body to expand said body by theinfluence of the absorbed liquid while maintaining the contourcharacteristics and thedetails of the article reproduced in said body,forming against the surface of the body which was formed against thearticle a reproduction of the article on an A enlarged scale, and,during the formation of the enlarged reproduction, exposing the bodyto asubstance for preventing evaporation of liquid from said body.

16. The steps in the method of making artiflcial teeth which compriseforming over the equivalent of a natural tooth a sheath of flexiblematerial adapted to absorb a liquid and to be expanded thereby, removingthe sheath from the tooth, treating said sheath with a liquid adapted tobe absorbed by said sheath to expand the sheath by the influence of theabsorbed liquid while maintaining the contour characteristics andthe'details of the tooth reproduced in said sheath.

- 17. The steps in the method of forming a reproduction of a surfacewhich comprise, reproducing the contour characteristics and details ofthe surface in a body of material adapted to absorb a fluid and to bechanged in size by the absorbed fluid, treating said body with a fluidadapted to be absorbedthereby to change the size of said body by theinfluence of the absorbed fluid while maintaining the contourcharacteristics and the details of the surface reproduced in said body.a

18. The steps in the method of forming a reproduction of a surface whichcomprise, reproducing the contour characteristics and details ofthesurface in a body of material adapted to absorb a fluid and to bechanged in size by the absorbed fluid, treating said body with a fluidadapted to be absorbed thereby to change the size of said body by theinfluence of the absorbed fluid while maintaining the contourcharacteristics and details of the surface reproduced in said body, andusing the reproduction of the surface produced in said body to form amember having a reproduction of said surface.

19. The steps in the method of forming a re-, production of a surfacewhich comprise, reproducing the contour characteristics and details ofthe surface in a body of flexible material adapted to absorb a fluid andto be changed in size by the absorbed fluid, treating said bodywith afluid fluid while maintaining the contour characteristics and thedetails of the surface reproduced in said body, and forming from saidflexible body of changed size a pattern having a reproduction of saidsurface. I

20. The steps in the method of forming a reproduction of an articlewhich comprise, taking an impression of the article, forming against theimpression a body of material adapted to absorb a fluid and to be'changed in size by the absorbed fluid, treating said body with a fluidadapted to. be absorbed thereby to change the size of said body by theinfluence of the absorbed fluid while maintaining the contourcharacteristics and the details of the surface formed against the 1mpression.

21. The steps in the method of forming a reproduction of an articlewhich comprise, taking an impression of the article, forming against theimpression a body of flexible material adapted to. absorb a fluid and tobe changed in size by the absorbed fluid, treating said body with afluid adapted to be absorbed thereby to change the size of said body bythe influence of the absorbed fluid while maintaining the contourcharacteristics and the details of the surface formed against theimpression, embedding the body of flexible material of changed size inan investment to reproduce the outen surface of said body in theinvestment, removing or eliminating said body from the investment toform a cavity, and forming a pattern in said cavity.

22. The process of producing articles in a flexible mold comprising thesteps of coating with rubber-like material an article of the same shapeas that to be produced, allowing the coating to dry and form a flexiblemold, then removing the article to permit the contraction of the mold,then treating said mold with a solution comprising an active swellingsolution and a diluting agent proportioned to expand same topredetermined flxed dimensions, then introducing hardenable reproductionmaterial into said mold, permitting said reproduction material toharden, and then removing said formed article from said mold.

23. The process of producing articles in a flexible mold comprising thesteps of coating with rubber-like material an article of the same shapeas that to be produced, allowing the coating to dry and form a flexiblemold, then removing the article to permit the contraction of the mold,then treating the outside surface of said mold with a solution havingthe ability to swell same to predetermined fixed dimensions, thenintroducing hardenable reproduction material into said mold, permittingsaid reproduction material to harden, and then removing said formedarticle from said mold.

24. The process of producing articles in a flexito harden, and thenremoving said formed article from said mold.

25. The process of producing articles in a flexible mold comprising thesteps of first coating the article to be reproduced with rubber-likematerial, permitting the material to dry and form a flexible mold, thenremoving the article from the flexible mold, then swelling said mold,then introducing a hardenable reproduction material into said mold, thenpermitting said reproduction material to harden, and then removing thereproduced article from the mold.

26. The process of producing articles in a flexible mold comprising thesteps of coating with rubber-like material an article of the same shapeas that to be produced, allowing the coating to dry and form a flexiblemold, then removing the article, then treating said mold with a solutionduction material from the having the ability to swell the same topredetermined fixed dimensions, then introducing hardenable reproductionmaterial into said mold;'permitting said reproduction material toharden, and then removing said formed article from said mold.

27. The process 01' producing articles comprising the steps of providinga flexible mold of rubber-like material, then increasing the size ofsaid mold by treating the same with a solution having the ability toswell said material, then introducing a hardenable reproduction materialinto said treated mold, permitting said material to harden, and thenremoving said molded repromold.

REINER W. ERDLE. HENRY SOLLER. PAUL H. BEIER.

